Apparatus for and method of forming vacuum packages

ABSTRACT

This disclosure relates to apparatus for forming vacuum packages and includes means defining a cavity adapted to receive a package having aperture means in a periphery thereof, means for temporarily sealing a flexible cover to the package periphery outboard of the aperture means, vacuum means for drawing a portion of the flexible cover overlying the aperture means away from the aperture means to form an access opening opening into the package between the flexible cover and the package periphery, means for withdrawing air from the package through the access opening and the aperture means incident to permanently sealing the flexible cover to the package periphery, and means for permanently sealing the flexible cover to the package periphery inboard of the aperture means.

I United States Patent [151 3,659,393 Richter 1 May 2, 1972 54]APPARATUS FOR AND METHOD OF FORMING VACUUM PACKAGES PrimaryExaminer-Travis S. McGehee Attorney-Diner, Brown, Ramik & Holt [72]Inventor: Joseph Richter, Fair Lawn, NJ. [73] Assignee: Royal PackagingEquipment, Inc., [57] ABSTRACT Mal/wood, This disclosure relates toapparatus for forming vacuum [22] Filed: May 28, 1970 packages andincludes means defining a cavity adapted to receive a package havingaperture means in a periphery PP 41,304 thereof, means for temporarilysealing a flexible cover to the package periphery outboard of theaperture means, vacuum [52] U S Cl 53/22 A 18/19 F 53/112 A means fordrawing a portion of the flexible cover overlying the [5 l] B65b 31/02aperture means away from the aperture means to form an ac- [58] Fieid AH2 A cess opening opening into the package between the flexible coverand the package periphery, means for withdrawing air [56] ReferencesCied from the package through the access opening and the aperture meansincident to permanently sealing the flexible cover to UNITED STATESPATENTS the package periphery, and means for permanently sealing the 3481 100 2/1969 B 53/112 A x flexible cover to the package peripheryinboard of the aperergstrom means. 3,061,984 11/1962 Mahaffy......53/112 A X 3,522,687 8/1970 Mahaffy ..53/112 A X 19 Claims, 6 DrawingFigures 67 62 60 63 v 64 6 SEE "I3 "[7 56.5

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APPARATUS FOR AND METHOD OF FORMING VACUUM PACKAGES A primary object ofthis invention is to provide apparatus for forming vacuum packages orpouches by providing two webs of heat sealable material, the first ofwhich is formed into a plurality of packages or pouches provided withone or more apertures in peripheries thereof. The packages are filled ina conventional manner and positioned within a cavity contoured to thegeneral configuration of the package. The second web is fed intooverlying relationship to the package after which'means are operativefor temporarily sealing the second web to the package periphery outboardof the aperture means. Thereafter a vacuum is drawn above thetemporarily sealed portion of the second web such that a portion of thesecond web is drawn away from the aperture to form an access openingopening into the package between the second web and the periphery of thepackage. It is through this access opening and the aperture that air iswithdrawn from the package after which means are provided to permanentlyseal the two webs to each other about the periphery but inboard of theaperture.

A further object of this invention is to provide novel apparatus of thetype described wherein permanent sealing means are reciprocably mountedwithin an evacuation chamber, and means are provided for relativelyreciprocating the evacuation chamber and the cavity.

A further object of this invention is to provide a novel apparatus ofthe type herebefore described wherein the evacuation chamber hascooperative inboard and outboard means for forming respective permanentand temporary seals, and said last-mentioned seals define a generallyannular passage into which opens a port adapted to be placed in fluidcommunication with a source of vacuum for drawing air outwardly of thepackage through the access opening and the aperture.

With the above and other objects in view that will hereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claimed subjectmatter, and the several views illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a schematic view of an apparatus constructed in accordancewith this invention, and illustrates a pair of heat scalable webs whichare formed into filled evacuated packages.

FIG. 2 is a cross-sectional view taken through an apparatus forevacuating each filled package, and illustrates the formation of atemporary peripheral seal between the webs outboard of an aperture in aperiphery of the lower web with a vacuum being drawn above the upper webto form an access opening through which air is withdrawn from thepackage.

FIG. 3 is a fragmentary sectional view similar to FIG. 2, andillustrates cooperative sealing means for forming a permanent peripheralseal inboard of the aperture formed in the package periphery.

FIG. 4 is a sectional view taken generally along line 44 of FIG. 2, andillustrates the manner in which two packages are simultaneouslyevacuated incident to being permanently sealed to form a pair ofevacuated packages.

FIG. 5 is a highly enlarged fragmentary sectional view of the encircledportion of FIG. 2. 7

.FIG. 6 is a fragmentary top plan view taken along the upper web of FIG.4 after the permanent seals have been made, and illustrates theparticular configuration thereof as well as the position of each sealinboard of the aperture associated therewith.

Reference is first made to FIG. 1 of the drawings which schematicallyillustrates a machine, generally designated by the reference numeral 10,for forming packages from a pair of webs ll, 12 drawn by conventionalmeans (not shown) from rolls 13, 14. The web 12 is heated by aconventional heater 15, and the heated portion is stepped into overlyingrelationship to a package-forming mold 16 which is adapted to bereciprocated vertically by conventional means (not shown), as isindicated by the double headed arrow 17. The packageforming mold 16includes one or more cavities (unnumbered) into which the heated portionof the web 12 is drawn to form one or more packages, each of which isgenerally designated by the reference numeral P. Thereafter the mold I6is retracted downwardly and the web 12 is again stepped to the leftduring which each package is filled with an appropriate product and aperipheral portion (unnumbered) of each package is provided with one ormore apertures A by means of a reciprocal piercing tool 18.

Each package is then positioned between a mechanism, generallydesignated by the reference numeral 20, for evacuating each package,directing an inert gas therein if desired, and heat sealing a portion ofthe web 11 to the periphery of each package inboard of the aperture A ina manner to be described more fully hereinafter. However, at this timeit will be pointed out that the mechanism 20 includes an upper member 21and a lower member 22 which are reciprocated between the closed positionillustrated in FIG. 1 and an open position at which the sealed packagescan be again step advanced to the left and severed to form individualpackages, as illustrated by the last package in FIG. 1.

Referring particularly to FIGS. 2 and 4 of the drawings, the mechanism20 includes the upper member 21 and the lower member 22, the latter ofwhich includes a base 23, a pair of long upstanding walls 24, 25, a pairof narrower end walls 26 27, and a central wall 28 medially thereof(FIG. 4). The walls 26, 28 and the left-hand portion of the walls 24,25, as viewed in FIG. 4, define a first cavity 30 while the walls 27,28, and the right-hand side of the walls 24, 25, as viewed in FIG. 4,define another cavity 31. The cavities 30, 31 are of a generallypolygonal cross-section but the shape thereof may be varied as might bethe number of cavities associates with each mechanism 20. That is,though lower member 22 of the mechanism 20 defines two cavities, thisnumber may also vary.

Upper inner surfaces of the walls 24 through 27 are cut away or notchedas at 32 to form an upper refacing shoulder (unnumbered), and seatedupon this shoulder is a generally rectangular frame 33 across the middleof which is secured a plate 38 (FIG. 4). As viewed from top elevationthe frame 33 and the plate 38 are of a block figure-8 configuration. Therectangular frame 33 carries upon its upper surface a pair ofrectangular yieldable cushioning or sealing members 34, 35. Whenoperated in a manner to be described hereinafter, seals S, S of a likeblock figure-8 configuration are obtained in the manner illustrated inFIG. 6.

It is to be noted that the wall 28 is secured by conventional fastenersto the plate 38 and to a rectangular flat plate 37. Due to thisconstruction the plate 37, the block 28, the plate 38, the frame 33, andthe rectangular cushioning members 34, 35 can be removed as a unit when,forv example, it is desired to form but a single package in a singlecavity as opposed to a pair of packages formed in the cavities 30, 31.When it is desired to form but one package another rectangular framecorresponding to the frame 33 is seated within the notch 32. However, asopposed to a pair of rectangular cushioning members 34, 35 the framecarries but a single rectangular cushioning member corresponding inlength and width generally to the over-all length and width of both ofthe cavities 30, 31. In this manner different numbers of packages can beformed by the mechanism of this invention merely by substituting frames33 of varying configurations carrying appropriately contoured cushioningmembers thereon.

Outboard of the notch 32 the walls 24 through 27 likewise have fixed toan uppermost end face thereof a yieldable cushioning or sealing member40 which again as viewed from above is of a rectangular outline anddefines with the member 34 an annular passage 41 which is likewise of arectangular configuration, as viewed from above in FIG. 4. A passage 42between the rectangular cushioning members 34, 35 above the plate 38merges at each end thereof with the annular passage 41 and thus thepassages 41, 42 are of a block figure-8 configuration, as viewed fromabove in FIG. 4.

The wall 25 is thicker than the walls 24, 26 and 27, and includes a pairof passages 45, 46 connected at their bottoms to a common passage 47which is connected by a flexible conduit 48 to a conventional vacuumsource (not shown). The passage 45 includes a port 50 opening into thecavity 30 (FIG. 4) and an upper port 51 (FIG. opening into the channel41 between the members 35, 40 and in substantial registration with theaperture A in the periphery (unnumbered) of the package housed withinthe cavity 30. The passage 46 likewise includes a port 52 opening intothe cavity 31 and an upper port (not shown) corresponding to the port 51of the passage 45 which likewise opensinto the passage 41 on the rightside of the wall 28, as viewed in FIG. 4. Though not illustrated, thisport is likewise in general registration with an aperture (not shown)formed in the periphery of the package housed within the cavity 31. Asis readily apparent in FIGS. 2, 4 and 5 of the drawings, air iswithdrawn from the exterior of the packages and the interior of thecavities 30, 31 through the respective ports 50, 52 and passages 45, 46while air is withdrawn from the interior of the packages through theapertures A, in the peripheries thereof, the passage 41 between themembers 35, 40, and the ports 51 of the passages 45, 46.

If it is desired to introduce an inert gas or similar gaseous mediuminto the interior of the packages, such may be conducted into thepassage 41 by means of a conduit 53 (FIG. 2), a passage 54 and a passage55 positioned between the passages 45, 46 and having an upper end (notshown) opening into the passage 41 between the members 35, 40. Gaseousmedium introduced into the passage 41 will, of course, enter thepackages through the apertures A in the package peripherres.

The upper member 21 includes a generally rectangular housing 60 having aperipheral skirt or wall 61 in overlying alignment with the sealingmember 40. The housing 60 defines a rectangular chamber 62 from whichair is adapted to be evacuated by means of a port 63 (FIG. 2) and aconduit 64 coupled to a conventional vacuum source (not shown).

A pair of cam actuated mechanical pistons or fluid motors 65, 66 areconventionally mounted atop the housing 60 and include respective pistonrods 67, 68 secured to a rectangular plate 70 having a central passage71. A pair of rectangular plates 72, 73 are removably secured to theplate 70 by fasteners (not shown), and each plate 72, 73 includes arectangular peripheral skirt 74, 75, respectively. The peripheral skirt74 of the plate 72 is in alignment along all four sides with the member34 while the peripheral skirt 75 of the plate 73 is in alignment withthe member 35 along all four sides thereof. The purpose of thisconfiguration is to form the generally rectangular permanent heat sealsS (FIG. 6) inboard of the apertures A in a manner to be described morefully hereinafter. For this purpose the skirts 74, 75 are heated by, forexample, calrod heaters 76, 77 carried by each of the members 72, 73.The electrical connections for the heaters 76, 77 are not shown but itis to be understood that the leads thereof maybe passed outwardly of thehousing 60 through the chamber 62 and an appropriate fitting (not shown)coupled to the threaded bore 78 shown in FIG. 2. The leads arepreferably long enough to accommodate for the up and down movement ofthe plate 70 under the influence of the cylinders 65, 66.

Before describing the operation of the mechanism immediatelyhereinafter, it is to be noted that the frame 33 while seated upon theshoulder 32 is maintained in its position by a plurality of balls 80seated in bores 81 positioned about the periphery of the walls 24through 27. The balls 80 are spring biased to engage a continuous groove82 formed in the outer periphery of the frame 33, and are biased tonormally seat in the groove 82 by a spring 83 seated upon a threadedplug (not shown). Thus, in normal operation the frame 33 is heldimmovable upon the shoulder 32 but in order to remove and replace thesame it is merely necessary to lift the frame 33 up wardly at which timethe spring 83 is compressed. When the frame 33 or a different frame isinserted into the cavities 30,

31 a like groove 82 thereon automatically receives each of the balls tomaintain such a new frame in its operative seated position upon theshoulder 32.

OPERATION Assuming that the members 21, 22 of the mechanism 20 are intheir spaced or retracted position, a pair of the filled pouches orpackages formed from the web 12 are advanced to a position above and inalignment with the cavities 30, 31 with, of course, a portion of the web11 in superimposed relationship thereto. The members 21, 22 are thenmoved to the closed position shown in FIG. 1 at which time a temporaryperipheral seal is effected between the bottom of the peripheral skirt61 and the member 40, as shown in FIG. 4. Air is then withdrawn from thechamber 62 through the conduit 64 and the port 63. The air is withdrawnthrough an annular space (unnumbered) between the inner surface of theskirt 61 and the outer periphery of the members 74, 75, as is indicatedby the unbroken unnumbered headed arrows in FIGS. 4 and 5. Air is alsodrawn upwardly through a gap (unnumbered) between the members 72, 73through the central passage 71, as best shown in FIG. 4. Thus, theentire upper web inboard of the temporary peripheral seal is drawnupwardly to the position shown in FIGS. 2 and 4 to form about the entireperiphery of the two webs inboard of the temporary seal a gap or spaceS, as is best illustrated in FIG. 5. By so lifting the portion of theinner web the apertures A are placed in fluid communication with theinterior of each of the packages through the space S which defines anaccess opening between the ports 51, 51 and the interior of eachpackage. Upon drawing a vacuum through the conduit 48 air within thechambers 30, 31 is withdrawn outwardly therefrom through the ports 50,52, in the manner heretofore described, but more importantly air in eachof the packages can now be withdrawn through the access opening S, eachof the apertures A, the passage 41, and each of the ports 51, 51 whichare substantially in registration with the apertures A, as is best shownin FIG. 5 by the unnumbered broken headed arrows. Once the packages havebeen completely evacuated, a gaseous medium may be inserted byconducting the same through the passages 54, 55 which, as heretoforenoted, open into the passage 41 and thus the gaseous medium is chargedinto the packages through the apertures A and the access openings S.

After the packages in the cavities 30, 31 have been charged with asuitable gaseous medium, the pistons 65, 66 are actuated simultaneouslyto lower the heated members 72, 73 to form the heat seals S by thecooperation of the rectangular heated peripheral skirts 74, 75 and thecushioning members 34, 35, thereby isolating each individual package,after which the system is returned to its normal stable condition, themechanism 20 is open, the webs 11, 12 are again advanced, and thereafterthe individual packages are severed and removed in the mannerdiagrammatically illustrated in FIG. 1.

While preferred forms and arrangements of parts have been shown inillustrating the invention, it is to be clearly understood that variouschanges in details and arrangement of parts may be made withoutdeparting from the spirit and scope of this disclosure.

I claim:

1. Apparatus for forming vacuum packages comprising means defining acavity adapted to receive a package having aperture means in a peripherythereof, means for temporarily sealing a flexible cover to the entirepackage periphery outboard of the aperture means, means for drawing aportion of said flexible cover overlying said aperture means away fromsaid aperture means to form an access opening into said package betweensaid flexible cover and said package periphery, and means forwithdrawing air from said package through said access opening and saidaperture means incident to permanently sealing said flexible cover tosaid package periphery inboard of said aperture means while the flexiblecover portion is held away from the aperture means by said drawingmeans.

2. The .apparatus as defined in claim 1 including means for permanentlysealing said flexible cover to said package periphery inboard of saidaperture means.

3. The apparatus as defined in claim 1 wherein said drawing meansincludes a source of vacuum.

4. The apparatus as defined in claim 1 including chamber means inboardof said sealing means and above said flexible cover, and said drawingmeans includes a source of vacuum in fluid communication with saidchamber means.

5. The apparatus as defined in claim 1 including means for permanentlysealing said flexible cover to said package periphery inboard of saidaperture means, said temporary and permanent sealing means being inspaced relationship to each other and defining chamber meanstherebetween, and said drawing means includes a source of vacuum influid communication with said chamber means.

6. The apparatus as defined in claim 1 wherein said withdrawing meansincludes a port in said cavity defining means in registration with saidaperture means.

7. The apparatus as defined in claim 1 wherein said drawing meansincludes a source of vacuum, said withdrawing means includes a port insaid cavity defining means in registration with said aperture means, andsaid port is inboard of said temporary sealing means.

8. The apparatus as defined in claim 7 including means for permanentlysealing said flexible cover to said package periphery inboard of saidaperture means, said temporary and permanent sealing means being inspaced relationship, and said port being in alignment with the spacebetween said temporary and permanent sealing means.

9. The apparatus as defined in claim 7 wherein the space defined by saidtemporary and permanent sealing means is of an annular configuration.

10. Apparatus for forming vacuum packages comprising a mold bodyincluding a peripheral wall defining a cavity adapted to receive apackage having aperture means in a periphery thereof, a port in saidperipheral wall adapted for registration with said aperture means, aclosure body including a peripheral wall defining an evacuation chamber,means for imparting relative movement to said bodies for opening andclosing the same, cooperative peripheral sealing means carried by saidperipheral walls for temporarily sealing a flexible cover to the entirepackage periphery outboard of said port and said aperture means, aportion of said evacuation chamber adjacent said port being outboardthereof whereby upon evacuation of said chamber a portion of saidflexible cover adjacent said evacuation chamber portion is drawn awayfrom said aperture means and said port, and means for evacuating airfrom said evacuation chamber while the flexible cover portion is drawnaway from said aperture means and said port by said evacuating means.

11. The apparatus as defined in claim 10 including cooperable peripheralsealing means in said evacuation chamber inboard of said temporarysealing means for permanently sealing said flexible cover to saidpackage periphery inboard of said aperture means and said port.

12. The apparatus as defined in claim 11 including means forreciprocating said permanent sealing means relative to said evacuationchamber and said temporary sealing means.

13. The apparatus as defined in claim 11 wherein said cooperativeperipheral temporary and permanent sealing means are in part eachdefined by a sealing member carried by said mold body peripheral wall,said sealing members define a generally annular passage therebetween,and said port opens into said passage.

14. The apparatus as defined in claim 12 wherein said cooperativeperipheral temporary and permanent sealing means are in part eachdefined by a sealing member carried by said mold body peripheral wall,said sealing members define a generally annular passage therebetween,and said port opens into said passage.

15. The apparatus as defined in claim 14 including means for withdrawingair from said package through said port and said aperture means.

16. A method of forming vacuum packages comprising the steps ofproviding a pair of webs, forming a package having an aperture in aperiphery thereof from a portion ofone of the webs, overlying a portionof the other web upon the package including the periphery thereof,temporarily sealing the two webs to each other along the entireperiphery and outboard of said aperture, drawing a vacuum above theother web at least adjacent said aperture whereby a portion of the otherweb overlying the aperture will be drawn away from an underlying portionof the one web periphery to form an access opening and withdrawing airfrom the package through the access opening and the aperture incident topermanently sealing the webs together inboard of said aperture whilesaid other web portion is drawn away from the access opening.

17. The method as defined in claim 16 including the step of permanentlysealing the webs together along the entire periphery and inboard of saidaperture.

18. A method of forming vacuum packages comprising the steps ofproviding a pair of webs, forming a package having an aperture from aportion of one of the webs, overlying a portion of the other web uponthe package, temporarily sealing the two webs to each other along theentire peripheries thereof and outboard of said aperture, drawing avacuum above the other web whereby a portion of the other web overlyingthe aperture will be drawn away from an underlying portion of the oneweb to form an access opening, and withdrawing air from the packagethrough the access opening and the aperture incident to permanentlysealing the webs together inboard of the aperture while said other webportion is drawn away from the access opening.

19. The method as defined in claim 18 including the step of permanentlysealing the webs together along the entire periphery and inboard of saidaperture.

1. Apparatus for forming vacuum packages comprising means defining a cavity adapted to receive a package having aperture means in a periphery thereof, means for temporarily sealing a flexible cover to the entire package periphery outboard of the aperture means, means for drawing a portion of said flexible cover overlying said aperture means away from said aperture means to form an access opening into said package between said flexible cover and said package periphery, and means for withdrawing air from said package through said access opening and said aperture means incident to permanently sealing said flexible cover to said package periphery inboard of said aperture means while the flexible cover portion is held away from the aperture means by said drawing means.
 2. The apparatus as defined in claim 1 including means for permanently sealing said flexible cover to said package periphery inboard of said aperture means.
 3. The apparatus as defined in claim 1 wherein said drawing means includes a source of vacuum.
 4. The apparatus as defined in claim 1 including chamber means inboard of said sealing means and above said flexible cover, and said drawing means includes a source of vacuum in fluid communication with said chamber means.
 5. The apparatus as defined in claim 1 including means for permanently sealing said flexible cover to said package periphery inboard of said aperture means, said temporary and permanent sealing means being in spaced relationship to each other and defining chamber means therebetween, and said drawing means includes a source of vacuum in fluid communication with said chamber means.
 6. The apparatus as defined in claim 1 wherein said withdrawing means includes a port in said cavity defining means in registration with said aperture means.
 7. The apparatus as defined in claim 1 wherein said drawing means includes a source of vacuum, said withdrawing means includes a port in said cavity defining means in registration with said aperture means, and said port is inboard of said temporary sealing means.
 8. The apparatus as defined in claim 7 including means for permanently sealing said flexible cover to said package periphery inboard of said aperture means, said temporary and permanent sealing means being in spaced relationship, and said port being in alignment with the space between said temporary and permanent sealing means.
 9. The apparatus as defined in claim 7 wherein the space defined by said temporary and permanent sealing means is of an annular configuration.
 10. Apparatus for forming vacuum packages comprising a mold body including a peripheral wall defining a cavity adapted to receive a package having aperture means in a periphery thereof, a port in said peripheral wall adapted for registration with said aperture means, a closure body including a peripheral wall defining an evacuation chamber, means for imparting relative Movement to said bodies for opening and closing the same, cooperative peripheral sealing means carried by said peripheral walls for temporarily sealing a flexible cover to the entire package periphery outboard of said port and said aperture means, a portion of said evacuation chamber adjacent said port being outboard thereof whereby upon evacuation of said chamber a portion of said flexible cover adjacent said evacuation chamber portion is drawn away from said aperture means and said port, and means for evacuating air from said evacuation chamber while the flexible cover portion is drawn away from said aperture means and said port by said evacuating means.
 11. The apparatus as defined in claim 10 including cooperable peripheral sealing means in said evacuation chamber inboard of said temporary sealing means for permanently sealing said flexible cover to said package periphery inboard of said aperture means and said port.
 12. The apparatus as defined in claim 11 including means for reciprocating said permanent sealing means relative to said evacuation chamber and said temporary sealing means.
 13. The apparatus as defined in claim 11 wherein said cooperative peripheral temporary and permanent sealing means are in part each defined by a sealing member carried by said mold body peripheral wall, said sealing members define a generally annular passage therebetween, and said port opens into said passage.
 14. The apparatus as defined in claim 12 wherein said cooperative peripheral temporary and permanent sealing means are in part each defined by a sealing member carried by said mold body peripheral wall, said sealing members define a generally annular passage therebetween, and said port opens into said passage.
 15. The apparatus as defined in claim 14 including means for withdrawing air from said package through said port and said aperture means.
 16. A method of forming vacuum packages comprising the steps of providing a pair of webs, forming a package having an aperture in a periphery thereof from a portion of one of the webs, overlying a portion of the other web upon the package including the periphery thereof, temporarily sealing the two webs to each other along the entire periphery and outboard of said aperture, drawing a vacuum above the other web at least adjacent said aperture whereby a portion of the other web overlying the aperture will be drawn away from an underlying portion of the one web periphery to form an access opening and withdrawing air from the package through the access opening and the aperture incident to permanently sealing the webs together inboard of said aperture while said other web portion is drawn away from the access opening.
 17. The method as defined in claim 16 including the step of permanently sealing the webs together along the entire periphery and inboard of said aperture.
 18. A method of forming vacuum packages comprising the steps of providing a pair of webs, forming a package having an aperture from a portion of one of the webs, overlying a portion of the other web upon the package, temporarily sealing the two webs to each other along the entire peripheries thereof and outboard of said aperture, drawing a vacuum above the other web whereby a portion of the other web overlying the aperture will be drawn away from an underlying portion of the one web to form an access opening, and withdrawing air from the package through the access opening and the aperture incident to permanently sealing the webs together inboard of the aperture while said other web portion is drawn away from the access opening.
 19. The method as defined in claim 18 including the step of permanently sealing the webs together along the entire periphery and inboard of said aperture. 